Fired tube conversion system and process

ABSTRACT

Disclosed is a process and system to convert acyclic C 5  feedstock to non-aromatic, cyclic C 5  hydrocarbon. A furnace and reactor tubes comprising a catalyst compound are disclosed. A process involving contacting acyclic C 5  feedstock with catalyst composition and obtaining cyclic C 5  hydrocarbon is also disclosed.

CROSS-REFERENCE OF RELATED APPLICATION

This invention claims priority to and the benefit of U.S. Ser. No.62/250,693, filed Nov. 4, 2015. This application relates to U.S. Ser.No. 62/250,674, filed Nov. 4, 2015.

FIELD OF THE INVENTION

This invention relates to fired tube reactors and their use in a processfor the conversion of acyclic C₅ feedstock to a product comprisingcyclic C₅ compounds.

BACKGROUND OF THE INVENTION

Cyclopentadiene (CPD) and its dimer dicyclopentadiene (DCPD) are highlydesired raw materials used throughout the chemical industry in a widerange of products such as polymeric materials, polyester resins,synthetic rubbers, solvents, fuels, fuel additives, etc. Cyclopentadiene(CPD) is currently a minor byproduct of liquid fed steam cracking (forexample, naphtha, and heavier feed). As existing and new steam crackingfacilities shift to lighter feeds, less CPD is produced while demand forCPD is rising. High cost due to supply limitations impacts the potentialend product use of CPD in polymers. More CPD-based polymer product couldbe produced if additional CPD could be produced at unconstrained ratesand preferably at a cost lower than recovery from steam cracking.Co-production of other cyclic C₅'s is also desirable. Cyclopentane andcyclopentene can have high value as solvents while cyclopentene may beused as a comonomer to produce polymers and as a starting material forother high value chemicals

It would be advantageous to be able to produce cyclic C₅ compounds,including CPD as the primary product from plentiful C₅ feedstock using acatalyst system to produce CPD while minimizing production of light(C⁴⁻) byproducts. While lower hydrogen content (for example, cyclics,alkenes, and dialkenes) could be preferred because the reactionendotherm is reduced and thermodynamic constraints on conversion areimproved, non-saturates are more expensive than saturate feedstock.Linear C₅ skeletal structure is preferred over branched C₅ skeletalstructures due to both reaction chemistry and the lower value of linearC₅ relative to branched C₅ (due to octane differences). An abundance ofC₅ is available from unconventional gas and shale oil, as well asreduced use in motor fuels due to stringent emissions requirements. C₅feedstock may also be derived from bio-feeds.

Various catalytic Dehydrogenation technologies are currently used toproduce mono and diolefins from C₃ and C₄ alkanes, but not cyclicmonoolefins or cyclic diolefins. A typical process uses Pt/Sn supportedon alumina as the active catalyst. Another useful process uses chromiaon alumina. See, B. V. Vora, “Development of Dehydrogenation Catalystsand Processes,” Topics in Catalysis, vol. 55, pp. 1297-1308, 2012; andJ. C. Bricker, “Advanced Catalytic Dehydrogenation Technologies forProduction of Olefins,” Topics in Catalysis, vol. 55, pp. 1309-1314,2012.

Still another common process uses Pt/Sn supported on Zn and/or Caaluminate to dehydrogenate propane. While these processes are successfulin dehydrogenating alkanes, they do not perform cyclization which iscritical to producing CPD. Pt—Sn/alumina and Pt—Sn/aluminate catalystsexhibit moderate conversion of n-pentane, but such catalysts have poorselectivity and yield to cyclic C₅ products.

Pt supported on chlorided alumina catalysts are used to reform lowoctane naphtha to aromatics, such as benzene and toluene. See, U.S. Pat.No. 3,953,368 (Sinfelt), “Polymetallic Cluster Compositions Useful asHydrocarbon Conversion Catalysts.” While these catalysts are effectivein dehydrogenating and cyclizing C₆ and higher alkanes to form C₆aromatic rings, they are less effective in converting acyclic C₅s tocyclic C₅s. These Pt supported on chlorided alumina catalysts exhibitlow yields of cyclic C₅ and exhibit deactivation within the first twohours of time on stream. Cyclization of C₆ and C₇ alkanes is aided bythe formation of an aromatic ring, which does not occur in C₅cyclization. This effect may be due in part to the much higher heat offormation for CPD, a cyclic C₅, as compared to benzene, a cyclic C₆, andtoluene, a cyclic C₇. This is also exhibited by Pt/Ir and Pt/Snsupported on chlorided alumina. Although these alumina catalysts performboth dehydrogenation and cyclization of C₆₊ species to form C₆ aromaticrings, a different catalyst will be needed to convert acyclic C₅ tocyclic C₅.

Ga-containing ZSM-5 catalysts are used in a process to produce aromaticsfrom light paraffins. A study by Kanazirev et al. showed n-pentane isreadily converted over Ga₂O₃/H-ZSM-5. See Kanazirev et al., “Conversionof C₈ aromatics and n-pentane over Ga₂O₃/H-ZSM-5 mechanically mixedcatalysts,” Catalysis Letters, vol. 9, pp. 35-42, 1991. No production ofcyclic C₅ was reported while upwards of 6 wt % aromatics were producedat 440° C. and 1.8 hr⁻¹ WHSV. Mo/ZSM-5 catalysts have also been shown todehydrogenate and/or cyclize paraffins, especially methane. See, Y. Xu,S. Liu, X. Guo, L. Wang, and M. Xie, “Methane activation without usingoxidants over Mo/HZSM-5 zeolite catalysts,” Catalysis Letters, vol. 30,pp. 135-149, 1994. High conversion of n-pentane using Mo/ZSM-5 wasdemonstrated with no production of cyclic C₅ and high yield to crackingproducts. This shows that ZSM-5-based catalysts can convert paraffins toa C₆ ring, but not necessarily to produce a C₅ ring.

U.S. Pat. No. 5,254,787 (Dessau) introduced the NU-87 catalyst used inthe dehydrogenation of paraffins. This catalyst was shown todehydrogenate C₂-C₆₊ to produce their unsaturated analogs. A distinctionbetween C₂₋₅ and C₆₊ alkanes was made explicit in this patent:dehydrogenation of C₂₋₅ alkanes produced linear or branched mono-olefinsor diolefins whereas dehydrogenation of C₆₊ alkanes yielded aromatics.U.S. Pat. No. 5,192,728 (Dessau) involves similar chemistry, but with atin-containing crystalline microporous material. As with the NU-87catalyst, C₅ dehydrogenation was only shown to produce linear orbranched, monoolefins or diolefins and not CPD.

U.S. Pat. No. 5,284,986 (Dessau) introduced a dual-stage process for theproduction of cyclopentane and cyclopentene from n-pentane. An examplewas conducted wherein the first stage involved dehydrogenation anddehydrocyclization of n-pentane to a mix of paraffins, monoolefins anddiolefins, and naphthenes over a Pt/Sn-ZSM-5 catalyst. This mixture wasthen introduced to a second-stage reactor consisting of Pd/Sn-ZSM-5catalyst where dienes, especially CPD, were converted to olefins andsaturates. Cyclopentene was the desired product in this process, whereasCPD was an unwanted byproduct. A comparative example was conducted onPt/Sn-ZSM-5 catalysts at varying temperatures, and is discussed below.

U.S. Pat. No. 2,438,398; U.S. Pat. No. 2,438,399; U.S. Pat. No.2,438,400; U.S. Pat. No. 2,438,401; U.S. Pat. No. 2,438,402; U.S. Pat.No. 2,438,403; and U.S. Pat. No. 2,438,404 (Kennedy) disclosedproduction of CPD from 1,3-pentadiene over various catalysts. Lowoperating pressures, low per pass conversion, and low selectivity makethis process undesirable. Additionally, 1,3-pentadiene is not a readilyavailable feedstock, unlike n-pentane. See also, Kennedy et al.,“Formation of Cyclopentadiene from 1,3-Pentadiene,” Industrial &Engineering Chemistry, vol. 42, pp. 547-552, 1950.

Fel'dblyum et al. in “Cyclization and dehydrocyclization of C₅hydrocarbons over platinum nanocatalysts and in the presence of hydrogensulfide,” Doklady Chemistry, vol. 424, pp. 27-30, 2009, reportedproduction of CPD from 1,3-pentadiene, n-pentene, and n-pentane. Yieldsto CPD were as high as 53%, 35%, and 21% for the conversion of1,3-pentadiene, n-pentene, and n-pentane respectively at 600° C. on 2%Pt/SiO₂. While initial production of CPD was observed, drastic catalystdeactivation within the first minutes of the reaction was observed.Experiments conducted on Pt-containing silica show moderate conversionof n-pentane over Pt—Sn/SiO₂, but with poor selectivity and yield tocyclic C₅ products. The use of H₂S as a 1,3-pentadiene cyclizationpromoter was presented by Fel'dblyum, infra, as well as in Marcinkowski,“Isomerization and Dehydrogenation of 1,3-Pentadiene,” M.S., Universityof Central Florida, 1977. Marcinkowski showed 80% conversion of1,3,-pentadiene with 80% selectivity to CPD with H₂S at 700° C. Hightemperature, limited feedstock, and potential of products containingsulfur that would later need scrubbing make this process undesirable.

López et al. in “n-Pentane Hydroisomerization on Pt Containing HZSM-5,HBEA and SAPO-11,” Catalysis Letters, vol. 122, pp. 267-273, 2008,studied reactions of n-pentane on Pt-containing zeolites includingH-ZSM-5. At intermediate temperatures (250-400° C.), they reportedefficient hydroisomerization of n-pentane on the Pt-zeolites with nodiscussion of cyclopentenes formation. It is desirable to avoid thisdeleterious chemistry as branched C₅ do not produce cyclic C₅ asefficiently as linear C₅, as discussed above.

Li et al. in “Catalytic dehydroisomerization of n-alkanes toisoalkenes,” Journal of Catalysis, vol. 255, pp. 134-137, 2008, alsostudied n-pentane dehydrogenation on Pt-containing zeolites in which Alhad been isomorphically substituted with Fe. These Pt/[Fe]ZSM-5catalysts were efficient dehydrogenating and isomerizing n-pentane, butunder the reaction conditions used, no cyclic C₅ were produced andundesirable skeletal isomerization occurred.

U.S. Pat. No. 5,633,421 discloses a process for dehydrogenating C₂-C₅paraffins to obtain corresponding olefins. Similarly, U.S. Pat. No.2,982,798 discloses a process for dehydrogenating an aliphatichydrocarbon containing 3 to 6, inclusive, carbon atoms. However, neitherU.S. Pat. No. 5,633,421 nor U.S. Pat. No. 2,982,798 disclose productionof CPD from acyclic C₅ hydrocarbons, which are desirable as feedstockbecause they are plentiful and low cost.

U.S. Pat. No. 5,243,122 describes a steam active catalytic processemploying a fixed catalyst bed for the dehydrogenation of alkanes toalkenes where the decline in catalyst activity is slowed by maintaininga substantially constant temperature for the reaction effluent whileallowing the average temperature of the fixed catalyst bed to riseduring a production period. Similarly, US 2012/0197054 discloses aprocess for dehydrogenation of alkanes in several reactors of theadiabatic, allothermal, or isothermal type or combinations thereof.

Further, many challenges exist in designing an on-purpose CPD productionprocess. For example, the reaction converting C₅ hydrocarbons to CPD isextremely endothermic and is favored by low pressure and hightemperature, but significant cracking of n-pentane and other C₅hydrocarbons can occur at relatively low temperature (e.g., 450° C.-500°C.). Further challenges include loss of catalyst activity due to cokingduring the process and further processing needed to remove coke from thecatalyst, and the inability to use oxygen-containing gas to directlyprovide heat input to the reactor without damaging the catalyst.

Hence, there remains a need for a process to convert acyclic C₅feedstock to non-aromatic, cyclic C₅ hydrocarbons, particularlycyclopentadiene, preferably at commercial rates and conditions. Further,there is a need for a catalytic process targeted for the production ofcyclopentadiene which generates cyclopentadiene in high yield fromplentiful C₅ feedstocks without excessive production of C⁴⁻ crackedproducts and with acceptable catalyst aging properties. Additionally,there is a need for processes and reactor systems for on-purpose CPDproduction from acyclic C₅ hydrocarbons, which address theabove-described challenges.

SUMMARY OF THE INVENTION

This invention relates to a process for converting acyclic C₅hydrocarbon to cyclic C₅ hydrocarbon, including but not limited to,cyclopentadiene (“CPD”), wherein the process comprises:

a) providing a furnace comprising parallel reactor tube(s), the reactortubes containing catalyst composition;

b) providing feedstock comprising acyclic C₅ hydrocarbon;

c) contacting the feedstock with the catalyst composition; and

d) obtaining a reactor effluent comprising cyclic C₅ hydrocarbonwherein, the cyclic C₅ hydrocarbon comprises cyclopentadiene.

In an aspect of the invention, i) the reactor tubes are positionedvertically so the feedstock is provided from the top and the reactoreffluent exits from the bottom and ii) the furnace comprises at leastone burner positioned near the top of the reactor tubes having a flameburning in a downward direction providing heat flux near the top that isgreater than heat flux near the bottom of the reactor tubes. In arelated aspect, a shield blocks at least a portion of the burner flame'sradiation from a bottom portion of the reactor tube. In another relatedaspect, the shield is a flue gas duct.

Another aspect of the invention relates to the reactor tubes having aninverse temperature profile.

Another aspect of the invention relates to the reactor tubes having anisothermal or substantially isothermal temperature profile.

Yet another aspect of the invention relates to transferring heat byconvection from flue gas to rejuvenation gas, regeneration gas, steam,and/or the feedstock in a convection section of the furnace.

Still another aspect of the invention relates to i) providing two ormore furnaces, each furnace comprising parallel reactor tube(s), thereactor tubes containing catalyst composition and ii) providing arejuvenation gas or a regeneration gas to one or more furnaces and, atthe same time, providing feedstock comprising acyclic C₅ hydrocarbons toa different one or more furnaces.

Another aspect of the invention relates to additional steps comprising:

a) discontinuing providing a feedstock comprising acyclic C₅hydrocarbons;

b) providing a rejuvenation gas comprising H₂;

c) contacting the rejuvenation gas with the catalyst composition toremove at least a portion of coke material on the catalyst composition;and

d) discontinuing providing a rejuvenation gas and resuming providing afeedstock comprising acyclic C₅ hydrocarbons.

Yet another aspect of the invention relates to additional stepscomprising:

a) discontinuing providing a feedstock comprising acyclic C₅hydrocarbons;

b) purging any combustible gas, including feedstock and reactor product,from the reactor tubes;

c) contacting a regeneration gas comprising an oxidizing material withthe catalyst composition to oxidatively remove at least a portion ofcoke material on the catalyst composition;

d) purging regeneration gas from the reactor tubes; and

e) discontinuing purging of regeneration gas and resuming providing afeedstock comprising acyclic C₅ hydrocarbons.

The invention also relates to a conversion system for converting acyclicC₅ hydrocarbon to cyclic C₅ hydrocarbon, wherein the conversion systemcomprises:

a) a feedstock stream comprising acyclic C₅ hydrocarbon;

b) a furnace comprising parallel reactor tube(s), the reactor tubescontaining catalyst composition; and

c) a reactor effluent stream comprising cyclic C₅ hydrocarbon producedby contacting the feedstock with the catalyst composition, wherein thecyclic C₅ hydrocarbon comprises cyclopentadiene.

An aspect of the invention relates to i) the reactor tubes arepositioned vertically, the feedstock is provided from the top, and thereactor effluent exits from the bottom of the reactor tubes and ii) thefurnace further comprises at least one burner positioned near the top ofthe reactor tubes having a flame burning in a downward directionproviding heat flux near the top that is greater than heat flux near thebottom of the reactor tubes. A related aspect of the invention is ashield blocking at least a portion of the burner flame's radiation froma bottom portion of the reactor tubes. Another related aspect of theinvention is wherein the shield is a flue gas duct.

Another aspect of the invention relates to fins or contours on theinside or outside of the reactor tubes promoting heat transfer from thetube wall to the catalyst composition.

Yet another aspect of the invention relates to mixing internalspositioned within the reactor tubes providing mixing in the radialdirection, wherein the mixing internals are positioned i) within a bedof the catalyst composition or ii) in portions of the reactor tubeseparating two or more zones of catalyst composition.

Still another aspect of the invention relates to the furnace furthercomprising a convection section providing heat transfer by convectionfrom flue gas to rejuvenation gas, regeneration gas, steam, and/or thefeedstock.

Another aspect of the invention relates to an additional one or morefurnaces, each furnace comprising parallel reactor tube(s), the reactortubes containing catalyst composition, enabling providing a rejuvenationgas or a regeneration gas to one or more furnaces and, at the same time,providing the feedstock comprising acyclic C₅ hydrocarbons to adifferent one or more furnaces.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an arrangement for multiple furnaces.

FIG. 2 is a diagram of a furnace.

FIG. 3 illustrates the total carbon yield of cyclic C₅ hydrocarbonsagainst time on stream (T.O.S.) in Example 3 while maintaining aninverse temperature profile (500 to 600° C. over 6 inches) or anisothermal temperature profile (600° C. throughout the 6 inches).

FIG. 4 illustrates the total carbon yield of C1-C4 hydrocarbons againstT.O.S. in Example 3 while maintaining an inverse temperature profile(500 to 600° C. over 6 inches) or an isothermal temperature profile(600° C. throughout the 6 inches).

FIG. 5 illustrates the site-time-yield (STY) of cyclic C5 hydrocarbons(i.e., the mols of cC5/mol of Pt/second) against T.O.S. in Example 5under a continuously-on-oil reactor operating strategy and anintermittent H₂ rejuvenation reactor operating strategy.

DETAILED DESCRIPTION OF THE INVENTION Definitions

For the purpose of this specification and the claims thereto, a numberof terms and phrases are defined below.

As used in the present disclosure and claims, the singular forms “a,”“an,” and “the” include plural forms unless the context clearly dictatesotherwise.

The term “and/or” as used in a phrase such as “A and/or B” herein isintended to include “A and B,” “A or B,” “A,” and “B.”

As used herein, the term “about” refers to a range of values of plus orminus 10% of a specified value. For example, the phrase “about 200”includes plus or minus 10% of 200, or from 180 to 220.

The term “saturates” includes, but is not limited to, alkanes andcycloalkanes.

The term “non-saturates” includes, but is not limited to, alkenes,dialkenes, alkynes, cycloalkenes and cyclodialkenes.

The term “cyclics C₅” or “cC₅” includes, but is not limited to,cyclopentane, cyclopentene, cyclopentadiene, and mixtures of two or morethereof. The term “cyclic C₅” or “cC₅” also includes alkylated analogsof any of the foregoing, e.g., methyl cyclopentane, methyl cyclopentene,and methyl cyclopentadiene. It should be recognized for purposes of theinvention that cyclopentadiene spontaneously dimerizes over time to formdicyclopentadiene via Diels-Alder condensation over a range ofconditions, including ambient temperature and pressure.

The term “acyclics” includes, but is not limited to, linear and branchedsaturates and non-saturates.

The term “aromatic” means a planar cyclic hydrocarbyl with conjugateddouble bonds, such as benzene. As used herein, the term aromaticencompasses compounds containing one or more aromatic rings, including,but not limited to, benzene, toluene and xylene, and polynucleararomatics (PNAs), which include naphthalene, anthracene, chrysene, andtheir alkylated versions. The term “C₆₊ aromatics” includes compoundsbased upon an aromatic ring having six or more ring atoms, including,but not limited to, benzene, toluene and xylene, and polynucleararomatics (PNAs), which include naphthalene, anthracene, chrysene, andtheir alkylated versions.

The term “BTX” includes, but is not limited to, a mixture of benzene,toluene, and xylene (ortho and/or meta and/or para).

The term “coke” includes, but is not limited to, a low hydrogen contenthydrocarbon that is adsorbed on the catalyst composition.

The term “C_(n)” means hydrocarbon(s) having n carbon atom(s) permolecule, wherein n is a positive integer.

The term “C_(n+)” means hydrocarbon(s) having at least n carbon atom(s)per molecule.

The term “C_(n−)” means hydrocarbon(s) having no more than n carbonatom(s) per molecule.

The term “C₅ feedstock” includes a feedstock containing n-pentane, suchas a feedstock which is predominately normal pentane and isopentane(also referred to as methylbutane), with smaller fractions ofcyclopentane and neopentane (also referred to as 2,2-dimethylpropane).

The term “hydrocarbon” means a class of compounds containing hydrogenbound to carbon, and encompasses (i) saturated hydrocarbon compounds,(ii) unsaturated hydrocarbon compounds, and (iii) mixtures ofhydrocarbon compounds (saturated and/or unsaturated), including mixturesof hydrocarbon compounds having different values of n.

As used herein, the term “oxygen-containing” means oxygen and compoundscontaining oxygen, including but not limited to O₂, CO₂, CO, H₂O, andoxygen-containing hydrocarbons such as alcohols, esters, ethers, etc.

All numbers and references to the Periodic Table of Elements are basedon the new notation as set out in Chemical and Engineering News, 63(5),27 (1985), unless otherwise specified.

The term “Group 10 metal” means an element in Group 10 of the PeriodicTable and includes Ni, Pd, and Pt.

The term “Group 11 metal” means an element in Group 11 of the PeriodicTable and includes, but is not limited to, Cu, Ag, Au, and a mixture oftwo or more thereof.

The term “Group 1 alkali metal” means an element in Group 1 of thePeriodic Table and includes, but is not limited to, Li, Na, K, Rb, Cs,and a mixture of two or more thereof, and excludes hydrogen.

The term “Group 2 alkaline earth metal” means an element in Group 2 ofthe Periodic Table and includes, but is not limited to, Be, Mg, Ca, Sr,Ba, and a mixture of two or more thereof.

The term “constraint index” is defined in U.S. Pat. No. 3,972,832 andU.S. Pat. No. 4,016,218, both of which are incorporated herein byreference.

As used herein, the term “molecular sieve of the MCM-22 family” (or“material of the MCM-22 family” or “MCM-22 family material” or “MCM-22family zeolite”) includes one or more of:

molecular sieves made from a common first degree crystalline buildingblock unit cell, which unit cell has the MWW framework topology. (A unitcell is a spatial arrangement of atoms, which if tiled inthree-dimensional space describes the crystal structure. Such crystalstructures are discussed in the “Atlas of Zeolite Framework Types,”Fifth edition, 2001, the entire content of which is incorporated asreference);

molecular sieves made from a common second degree building block, beinga 2-dimensional tiling of such MWW framework topology unit cells,forming a monolayer of one unit cell thickness, preferably one c-unitcell thickness;

molecular sieves made from common second degree building blocks, beinglayers of one or more than one unit cell thickness, wherein the layer ofmore than one unit cell thickness is made from stacking, packing, orbinding at least two monolayers of one unit cell thickness. The stackingof such second degree building blocks may be in a regular fashion, anirregular fashion, a random fashion, or any combination thereof; and

molecular sieves made by any regular or random 2-dimensional or3-dimensional combination of unit cells having the MWW frameworktopology.

The MCM-22 family includes those molecular sieves having an X-raydiffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15,3.57±0.07 and 3.42±0.07 Angstrom. The X-ray diffraction data used tocharacterize the material are obtained by standard techniques using theK-alpha doublet of copper as incident radiation and a diffractometerequipped with a scintillation counter and associated computer as thecollection system.

As used herein, the term “molecular sieve” is used synonymously with theterm “microporous crystalline material” or “zeolite.”

As used herein, the term “carbon selectivity” means the moles of carbonin the respective cyclic C₅, CPD, C₁, and C₂₋₄ formed divided by totalmoles of carbon in the pentane converted. The phrase “a carbonselectivity to cyclic C₅ of at least 30%” means that 30 moles of carbonin the cyclic C₅ is formed per 100 moles of carbon in the pentaneconverted.

As used herein, the term “conversion” means the moles of carbon in theacyclic C₅ feedstock that is converted to a product. The phrase “aconversion of at least 70% of said acyclic C₅ feedstock to said product”means that at least 70% of the moles of said acyclic C₅ feedstock wasconverted to a product.

As used herein, the term “reactor system” refers to a system includingone or more reactors and all necessary and optional equipment used inthe production of cyclopentadiene.

As used herein, the term “reactor” refers to any vessel(s) in which achemical reaction occurs. Reactor includes both distinct reactors, aswell as reaction zones within a single reactor apparatus and asapplicable, reactions zones across multiple reactors. In other words,and as is common, a single reactor may have multiple reaction zones.Where the description refers to a first and second reactor, the personof ordinary skill in the art will readily recognize such referenceincludes two reactors, as well as a single reactor having first andsecond reaction zones. Likewise, a first reactor effluent and a secondreactor effluent will be recognized to include the effluent from thefirst reaction zone and the second reaction zone of a single reactor,respectively.

For purposes of the invention, 1 psi is equivalent to 6.895 kPa.Particularly, 1 psia is equivalent to 1 kPa absolute (kPa-a). Likewise,1 psig is equivalent to 6.895 kPa gauge (kPa-g).

This invention relates to a process for converting acyclic C₅hydrocarbon to cyclic C₅ hydrocarbon, wherein the process comprises:providing a furnace comprising parallel reactor tube(s), the reactortubes containing catalyst composition; providing feedstock comprisingacyclic C₅ hydrocarbon; contacting the feedstock with the catalystcomposition; and obtaining a reactor effluent comprising cyclic C₅hydrocarbon wherein, the cyclic C₅ hydrocarbon comprisescyclopentadiene. Aspects of the conversion system and process can enablemaintaining an inverse temperature profile in the reactor tubes whichmay advantageously minimize carbonaceous material formation. Aspects ofthe conversion system and process can alternatively enable maintainingan isothermal or substantially isothermal temperature profile in thereactor tubes, which may advantageously increase catalyst efficiency andimprove product yield by reducing the amount of low value, cracked(i.e., C⁴⁻) byproduct.

Other aspects of the invention permit operating the reactor outlet at asub-atmospheric pressure to enhance formation of cyclic C₅ product.

Feedstock

Acyclic C₅ feedstock useful herein is obtainable from crude oil ornatural gas condensate, and can include cracked C₅ (in various degreesof unsaturation: alkenes, dialkenes, alkynes) produced by refining andchemical processes, such as fluid catalytic cracking (FCC), reforming,hydrocracking, hydrotreating, coking, and steam cracking.

In one or more embodiments, the acyclic C₅ feedstock useful in theprocess of this invention comprises pentane, pentene, pentadiene, andmixtures of two or more thereof. Preferably, in one or more embodiments,the acyclic C₅ feedstock comprises at least about 50 wt %, or 60 wt %,or 75 wt %., or 90 wt % n-pentane, or in the range from about 50 wt % toabout 100 wt % n-pentane.

The acyclic C₅ feedstock optionally does not comprise C₆ aromaticcompounds, such as benzene, preferably C₆ aromatic compounds are presentat less than 5 wt %, preferably less than 1 wt %, preferably present atless than 0.01 wt %, preferably at 0 wt %.

The acyclic C₅ feedstock optionally does not comprise benzene, toluene,or xylene (ortho, meta, or para), preferably the benzene, toluene, orxylene (ortho, meta, or para) compounds are present at less than 5 wt %,preferably less than 1 wt %, preferably present at less than 0.01 wt %,preferably at 0 wt %.

The acyclic C₅ feedstock optionally does not comprise C₆₊ aromaticcompounds, preferably C₆₊ aromatic compounds are present at less than 5wt %, preferably less than 1 wt %, preferably present at less than 0.01wt %, preferably at 0 wt %.

The acyclic C₅ feedstock optionally does not comprise C₆₊ compounds,preferably C₆₊ compounds are present at less than 5 wt %, preferablyless than 1 wt %, preferably present at less than 0.01 wt %, preferablyat 0 wt %.

Preferably, the C₅ feedstock is substantially free of oxygen-containingcompounds. “Substantially free” used in this context means the feedstockcomprises less than about 1.0 wt. %, based upon the weight of the feed,e.g., less than about 0.1 wt. %, less than about 0.01 wt. %, less thanabout 0.001 wt. %, less than about 0.0001 wt. %, less than about 0.00001wt. % oxygen-containing compounds.

Preferably, a hydrogen co-feedstock comprising hydrogen and, optionally,light hydrocarbons, such as C₁-C₄ hydrocarbons, is also fed into thefirst reactor. Preferably, at least a portion of the hydrogenco-feedstock is admixed with the C₅ feedstock prior to being fed intothe first reactor. The presence of hydrogen in the feed mixture at theinlet location, where the feed first comes into contact with thecatalyst, prevents or reduces the formation of coke on the catalystparticles. C₁-C₄ hydrocarbons may also be co-fed with the C₅.

Acyclic C₅ Conversion Process

The first aspect of the invention is a process for conversion of anacyclic C₅ feedstock to a product comprising cyclic C₅ compounds. Theprocess comprising the steps of contacting said feedstock and,optionally, hydrogen under acyclic C₅ conversion conditions in thepresence of one or more catalyst compositions, including but not limitedto the catalyst compositions described herein, to form said product.

The second aspect of the invention is also a process for conversion ofan acyclic C₅ feedstock to a product comprising cyclic C₅ compounds, theprocess comprising the steps of contacting said feedstock and,optionally, hydrogen under acyclic C₅ conversion conditions in thepresence of one or more catalyst compositions, including but not limitedto the catalyst compositions described herein, to form said product.

In one or more embodiments, the product of the process for conversion ofan acyclic C₅ feedstock comprises cyclic C₅ compounds. The cyclic C₅compounds comprise one or more of cyclopentane, cyclopentene,cyclopentadiene, and includes mixtures thereof. In one or moreembodiments, the cyclic C₅ compounds comprise at least about 20 wt %, or30 wt %, or 40 wt %, or 50 wt % cyclopentadiene, or in the range of fromabout 10 wt % to about 80 wt %, alternately 10 wt % to 80 wt %.

In one or more embodiments, the acyclic C₅ conversion conditions includeat least a temperature, a reactor outlet pressure, a reactor pressuredrop (reactor inlet pressure−reactor outlet pressure) and a weighthourly space velocity (WHSV). The temperature is in the range of about450° C. to about 800° C., or in the range from about 450° C. to about650° C., preferably, in the range from about 450° C. to about 600° C.The reactor outlet pressure in the range of about 1 to about 50 psia, orin the range from about 4 to about 25 psia, preferably in the range ofabout 4 to about 10 psia. Advantageously, operating the reactor outletat a sub-atmospheric pressure enhances formation of cyclic C₅ product.The reactor pressure drop is in the range of about 1 to about 100 psi,or in the range of from about 1 to about 75 psi, preferably about 1 toabout 45 psi, such as about 5 to about 45 psi. The weight hourly spacevelocity in the range from about 1 to about 1000 hr⁻¹, or in the rangefrom about 1 to about 100 hr⁻¹, preferably from about 2 to about 20hr⁻¹. Such conditions include a molar ratio of the optional hydrogenco-feed to the acyclic C₅ feedstock in the range of about 0 to 3, or inthe range from about 1 to about 2. Such conditions may also includeco-feed C₁-C₄ hydrocarbons with the acyclic C₅ feed. Preferably co-feed(if present), whether comprising hydrogen, C₁-C₄ hydrocarbons or both,is substantially free of oxygen-containing compounds. “Substantiallyfree” used in this context means the co-feed comprises less than about1.0 wt. %, based upon the weight of the co-feed, e.g., less than about0.1 wt. %, less than about 0.01 wt. %, less than about 0.001 wt. %, lessthan about 0.0001 wt. %, less than about 0.00001 wt. % oxygen-containingcompounds.

In one or more embodiments, this invention relates to a process forconversion of n-pentane to cyclopentadiene comprising the steps ofcontacting n-pentane and, optionally, hydrogen (if present, typically H₂is present at a ratio to n-pentane of 0.01 to 3.0) with one or morecatalyst compositions, including, but not limited to, the catalystcompositions described herein, to form cyclopentadiene at a reactoroutlet temperature of 550° C. to 650° C., a reactor outlet pressure of 4to about 20 psia, a reactor pressure drop of about 1 to about 45 psi,such as about 5 to about 45 psi, and a weight hourly space velocity of 2to about 20 hr⁻¹. Preferably, the reactor tubes, during contactingfeedstock with catalyst composition, have a pressure drop measured fromreactor inlet to reactor outlet of less than 20 psi, more preferablyless than 5 psi.

Catalyst compositions useful herein include microporous crystallinemetallosilicates, such as crystalline aluminosilicates, crystallineferrosilicates, or other metal containing crystalline silicates (such asthose where the metal or metal-containing compound is dispersed withinthe crystalline silicate structure and may or may not be a part of thecrystalline framework). Microporous crystalline metallosilicateframework types useful as catalyst compositions herein include, but arenot limited to, MWW, MFI, LTL, MOR, BEA, TON, MTW, MTT, FER, MRE, MFS,MEL, DDR, EUO, and FAU.

Particularly suitable microporous metallosilicates for use hereininclude those of framework type MWW, MFI, LTL, MOR, BEA, TON, MTW, MTT,FER, MRE, MFS, MEL, DDR, EUO, and FAU (such as zeolite beta, mordenite,faujasite, Zeolite L, ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48,ZSM-50, ZSM-57, ZSM-58, and MCM-22 family materials) where one or moremetals from groups 8, 11, and 13 of the Periodic Table of the Elements(preferably one or more of Fe, Cu, Ag, Au, B, Al, Ga, and/or In) areincorporated in the crystal structure during synthesis or impregnatedpost crystallization. It is recognized that a metallosilicate may haveone of more metals present and, for example, a material may be referredto as a ferrosilicate, but it will most likely still contain smallamounts of aluminum.

The microporous crystalline metallosilicates preferably have aconstraint index of less than 12, alternately from 1 to 12, alternatelyfrom 3 to 12. Aluminosilicates useful herein have a constraint index ofless than 12, such as 1 to 12, alternately 3 to 12, and include, but arenot limited to Zeolite beta, mordenite, faujasite, Zeolite L, ZSM-5,ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, ZSM-57, ZSM-58, MCM-22family materials, and mixtures of two or more thereof. In a preferredembodiment, the crystalline aluminosilicate has a constraint index ofabout 3 to about 12 and is ZSM-5.

ZSM-5 is described in U.S. Pat. No. 3,702,886. ZSM-11 is described inU.S. Pat. No. 3,709,979. ZSM-22 is described in U.S. Pat. No. 5,336,478.ZSM-23 is described in U.S. Pat. No. 4,076,842. ZSM-35 is described inU.S. Pat. No. 4,016,245. ZSM-48 is described in U.S. Pat. No. 4,375,573.ZSM-50 is described in U.S. Pat. No. 4,640,829. ZSM-57 is described inU.S. Pat. No. 4,873,067. ZSM-58 is described in U.S. Pat. No. 4,698,217.Constraint index and a method for its determination are described inU.S. Pat. No. 4,016,218. The entire contents of each of theaforementioned patents are incorporated herein by reference.

The MCM-22 family material is selected from the group consisting ofMCM-22, PSH-3, SSZ-25, MCM-36, MCM-49, MCM-56, ERB-1, EMM-10, EMM-10-P,EMM-12, EMM-13, UZM-8, UZM-8HS, ITQ-1, ITQ-2, ITQ-30, and mixtures oftwo or more thereof.

Materials of the MCM-22 family include MCM-22 (described in U.S. Pat.No. 4,954,325), PSH-3 (described in U.S. Pat. No. 4,439,409), SSZ-25(described in U.S. Pat. No. 4,826,667), ERB-1 (described in EP 0 293032), ITQ-1 (described in U.S. Pat. No. 6,077,498), and ITQ-2 (describedin WO 97/17290), MCM-36 (described in U.S. Pat. No. 5,250,277), MCM-49(described in U.S. Pat. No. 5,236,575), MCM-56 (described in U.S. Pat.No. 5,362,697), and mixtures of two or more thereof. Related zeolites tobe included in the MCM-22 family are UZM-8 (described in U.S. Pat. No.6,756,030) and UZM-8HS (described in U.S. Pat. No. 7,713,513), both ofwhich are also suitable for use as the molecular sieve of the MCM-22family.

In one or more embodiments, the crystalline metallosilicate has an Si/Mmolar ratio (where M is a group 8, 11, or 13 metal) greater than about3, or greater than about 25, or greater than about 50, or greater thanabout 100, or greater than about 400, or in the range from about 100 toabout 2,000, or from about 100 to about 1,500, or from about 50 to about2,000, or from about 50 to about 1,200.

In one or more embodiments, the crystalline aluminosilicate has anSiO₂/Al₂O₃ molar ratio greater than about 3, or greater than about 25,or greater than about 50, or greater than about 100, or greater thanabout 400, or in the range from about 100 to about 400, for from about100 to about 500, or from about 25 to about 2,000, or from about 50 toabout 1,500, or from about 100 to about 1,200, or from about 100 toabout 1000.

In another embodiment of the invention, the microporous crystallinemetallosilicate (such as an aluminosilicate) is combined with a Group 10metal or metal compound, and, optionally, one, two, three, or more Group1, 2, or 11 metals or metal compounds.

In one or more embodiments, the Group 10 metal includes, or is selectedfrom the group consisting of, Ni, Pd, and Pt, preferably Pt. The Group10 metal content of said catalyst composition is at least 0.005 wt %,based on the weight of the catalyst composition. In one or moreembodiments, the Group 10 content is in the range from about 0.005 wt %to about 10 wt %, or from about 0.005 wt % up to about 1.5 wt %, basedon the weight of the catalyst composition.

In one or more embodiments, the Group 1 alkali metal includes, or isselected from the group consisting of, Li, Na, K, Rb, Cs, and mixturesof two or more thereof, preferably Na; hydrogen is excluded.

In one or more embodiments, the Group 2 alkaline earth metal is selectedfrom the group consisting of Be, Mg, Ca, Sr, Ba, and mixtures of two ormore thereof.

In one or more embodiments, the Group 1 alkali metal is present as anoxide and the metal is selected from the group consisting of Li, Na, K,Rb, Cs, and mixtures of two or more thereof. In one or more embodiments,the Group 2 alkaline earth metal is present as an oxide and the metal isselected from the group consisting of Be, magnesium, calcium, Sr, Ba,and mixtures of two or more thereof. In one or more embodiments, theGroup 1 alkali metal is present as an oxide and the metal is selectedfrom the group consisting of Li, Na, K, Rb, Cs, and mixtures of two ormore thereof; and the Group 2 alkaline earth metal is present as anoxide and the metal is selected from the group consisting of Be,magnesium, calcium, Sr, Ba, and mixtures of two or more thereof.

In one or more embodiments, the Group 11 metal includes, or is selectedfrom the group consisting of, silver, gold, copper, preferably silver orcopper. The Group 11 metal content of said catalyst composition is atleast 0.005 wt %, based on the weight of the catalyst composition. Inone or more embodiments, the Group 11 content is in the range from about0.005 wt % to about 10 wt %, or from about 0.005 wt % up to about 1.5 wt%, based on the weight of the catalyst composition.

In one or more embodiments, the catalyst composition has an Alpha Value(as measured prior to the addition of the Group 10 metal, preferablyplatinum) of less than about 25, preferably of less than about 15.

In one or more embodiments of aluminosilicates, the molar ratio of saidGroup 1 alkali metal to Al is at least about 0.5, or from at least about0.5 up to about 3, preferably at least about 1, more preferably at leastabout 2.

In one or more embodiments of aluminosilicates, the molar ratio of saidGroup 2 alkaline earth metal to Al is at least about 0.5, or from atleast about 0.5 up to about 3, preferably at least about 1, morepreferably at least about 2.

In one or more embodiments, the molar ratio of said Group 11 metal toGroup 10 metal is at least about 0.1, or from at least about 0.1 up toabout 10, preferably at least about 0.5, more preferably at leastabout 1. In one or more embodiments, the Group 11 alkaline earth metalis present as an oxide and the metal is selected from the groupconsisting of gold, silver, and copper, and mixtures of two or morethereof.

In one or more embodiments, the use of the catalyst compositions of thisinvention provides a conversion of at least about 70%, or at least about75%, or at least about 80%, or in the range from about 60% to about 80%,of said acyclic C₅ feedstock under acyclic C₅ conversion conditions ofan n-pentane containing feedstock with equimolar H₂, a temperature inthe range of about 550° C. to about 600° C., an n-pentane partialpressure between 3 and 10 psia at the reactor inlet, and an n-pentaneweight hourly space velocity of 10 to 20 hr-1.

In one or more embodiments, the use of any one of the catalystcompositions of this invention provides a carbon selectivity to cyclicC₅ compounds of at least about 30%, or at least about 40%, or at leastabout 50%, or in the range from about 30% to about 80%, under acyclic C₅conversion conditions including an n-pentane feedstock with equimolarH₂, a temperature in the range of about 550° C. to about 600° C., ann-pentane partial pressure between 3 and 10 psia at the reactor inlet,and an n-pentane weight hourly space velocity between 10 and 20 hr-1.

In one or more embodiments, the use of any one of the catalystcompositions of this invention provides a carbon selectivity tocyclopentadiene of at least about 30%, or at least about 40%, or atleast about 50%, or in the range from about 30% to about 80%, underacyclic C₅ conversion conditions including an n-pentane feedstock withequimolar H₂, a temperature in the range of about 550° C. to about 600°C., an n-pentane partial pressure between 3 and 10 psia at the reactorinlet, and an n-pentane weight hourly space velocity between 10 and 20hr-1.

The catalyst compositions of this invention can be combined with amatrix or binder material to render them attrition resistant and moreresistant to the severity of the conditions to which they will beexposed during use in hydrocarbon conversion applications. The combinedcompositions can contain 1 to 99 wt % of the materials of the inventionbased on the combined weight of the matrix (binder) and material of theinvention. The relative proportions of microcrystalline material andmatrix may vary widely, with the crystal content ranging from about 1 toabout 90 wt % and more usually, particularly when the composite isprepared in the form of beads, extrudates, pills, oil drop formedparticles, spray dried particles, etc., in the range of about 2 to about80 wt % of the composite.

Catalyst composition shape and design are preferably configured tominimize pressure drop, increase heat transfer, and minimize masstransport phenomena. Catalyst composition may be formed into particlesthat are random loaded into the reactor or may be formed into structuredcatalyst shapes within the reactor.

Suitable catalyst particle shapes and designs are described in WO2014/053553, which is incorporated herein by reference. The catalystcomposition may be an extrudate with a diameter of 2 mm to 20 mm, forexample, 2 mm to 10 mm, or 5 mm to 15 mm. Optionally, the catalystcomposition cross section may be shaped with one or more lobes and/orconcave sections. Additionally, the catalyst composition lobes and/orconcave sections may be spiraled. The catalyst composition may be anextrudate with a diameter of 2 mm to 20 mm, for example, 2 mm to 10 mm,or 5 mm to 15 mm; and the catalyst composition cross section may beshaped with one or more lobes and/or concave sections; and the catalystcomposition lobes and/or concave sections may be spiraled. For fixed bedreactors (fired tube, convective tube, and cyclic) lobed, concave,spiral, etc., particle shapes are particularly useful and for fluid bedreactors spherical particle shapes are particularly useful. Preferably,particles for a fixed bed (e.g., cyclic fixed bed reactor, fired tubesreactor, convectively heated tubes reactor, etc.) are typically anextrudate with a diameter of 2 mm to 20 mm; and the catalyst compositioncross section may be shaped with one or more lobes and/or concavesections; and the catalyst composition lobes and/or concave sections maybe spiraled. Shapes may also include holes or perforations in the shapesto increase voidage and improve mass transfer.

Structured catalyst shape examples include a coating of catalyst ontothe inner wall of the reactor and/or onto other formed inorganic supportstructures. Suitable formed inorganic support structures may be metallicor ceramic. Preferred ceramics are those with high thermal conductivity,e.g., silicon carbide, aluminum nitride, boron carbide, and siliconnitride. Suitable formed inorganic support structures may be orderedstructures, such as extruded ceramic monoliths and extruded or rolledmetal monoliths. Often, suitable formed inorganic support structures mayalso include ceramic or metal foams and 3D printed structures. Thecoating of active catalyst may be applied to the support structures viawash coating or other means known in the art. Preferably, the coatingthickness is less than 1,000 microns; more preferably less than 500microns; most preferably between 100 and 300 microns.

During the use of the catalyst compositions in the processes of thisinvention, coke may be deposited on the catalyst compositions, wherebysuch catalyst compositions lose a portion of their catalytic activityand become deactivated. The deactivated catalyst compositions may beregenerated by techniques including high pressure hydrogen treatment andcombustion of coke on the catalyst compositions with oxygen, such as airor O₂ gas.

Useful catalyst compositions comprise a crystalline aluminosilicate orferrosilicate, which is optionally combined with one, two, or moreadditional metals or metal compounds. Preferred combinations include:

1) a crystalline aluminosilicate (such as ZSM-5 or Zeolite L) combinedwith a Group 10 metal (such as Pt), a Group 1 alkali metal (such assodium or potassium), and/or a Group 2 alkaline earth metal;

2) a crystalline aluminosilicate (such as ZSM-5 or Zeolite L) combinedwith a Group 10 metal (such as Pt) and a Group 1 alkali metal (such assodium or potassium);

3) a crystalline aluminosilicate (such as a ferrosilicate or an irontreated ZSM-5) combined with a Group 10 metal (such as Pt) and a Group 1alkali metal (such as sodium or potassium);

4) a crystalline aluminosilicate (Zeolite L) combined with a Group 10metal (such as Pt) and a Group 1 alkali metal (such as potassium); and

5) a crystalline aluminosilicate (such as ZSM-5) combined with a Group10 metal (such as Pt), a Group 1 alkali metal (such as sodium), and aGroup 11 metal (such as silver or copper).

Another useful catalyst composition is a group 10 metal (such as Ni, Pd,and Pt, preferably Pt) supported on silica (e.g. silicon dioxide)modified by a Group 1 alkali metal silicate (such as Li, Na, K, Rb,and/or Cs silicates) and/or a Group 2 alkaline earth metal silicate(such as Mg, Ca, Sr, and/or Ba silicates), preferably potassiumsilicate, sodium silicate, calcium silicate and/or magnesium silicate,preferably potassium silicate and/or sodium silicate. The Group 10 metalcontent of the catalyst composition is at least 0.005 wt %, based on theweight of the catalyst composition, preferably, in the range from about0.005 wt % to about 10 wt %, or from about 0.005 wt % up to about 1.5 wt%, based on the weight of the catalyst composition. The silica (SiO2)may be any silica typically used as catalyst support such as thosemarketed under the tradenames of DAVISIL 646 (Sigma Aldrich), Davison952, DAVISON 948 or Davison 955 (Davison Chemical Division of W.R. Graceand Company).

In various aspects, the catalyst material (and optional matrix material)may have an average diameter of about 5 μm to about 50 mm, such as about25 μm to about 3500 μm. Preferably, the catalyst material (and optionalmatrix or binder) may have an average diameter of about 25 μm to about1200 μm, more preferably about 50 μm to about 1000 μm, more preferablyabout 10 μm to about 500 μm, more preferably about 30 μm to about 400μm, more preferably about 40 μm to about 300 μm.

“Average diameter” for particles in the range of 1 to 3500 μm isdetermined using a Mastersizer™ 3000 available from Malvern Instruments,Ltd., Worcestershire, England. Unless otherwise stated, particle size isdetermined at D50. D50 is the value of the particle diameter at 50% inthe cumulative distribution. For example, if D50=5.8 um, then 50% of theparticles in the sample are equal to or larger than 5.8 um and 50% aresmaller than 5.8 um. (In contrast, if D90=5.8 um, then 10% of theparticles in the sample are larger than 5.8 um and 90% are smaller than5.8 um.) “Average diameter” for particles in the range of 3 mm to 50 mmis determined using a micrometer on a representative sample of 100particles.

For more information on useful catalyst compositions, please seeapplications:

1) U.S. Ser. No. 62/250,675, filed Nov. 4, 2015;

2) U.S. Ser. No. 62/250,681, filed Nov. 4, 2015;

3) U.S. Ser. No. 62/250,688, filed Nov. 4, 2015;

4) U.S. Ser. No. 62/250,695, filed Nov. 4, 2015; and

5) U.S. Ser. No. 62/250,689, filed Nov. 4, 2015; which are incorporatedherein by reference.

Conversion System

The feedstock is fed into a conversion system comprising a furnace andparallel reactor tube(s) positioned within a radiant section of thefurnace. Optionally, the feedstock is fed to an adiabatic lead reactionzone prior to being fed to the furnace. For more information on the useof an adiabatic lead reaction zone, please see U.S. Ser. No. 62/250,697,filed Nov. 4, 2015, which is incorporated herein by reference. While anyknown radiant furnace reactor tube configuration may be used, preferablythe furnace comprises multiple parallel reactor tubes. Suitable furnacereactor tube configurations include those described in U.S. Pat. No.5,811,065; U.S. Pat. No. 5,243,122; U.S. Pat. No. 4,973,778; US2012/0060824; and US 2012/0197054, which are entirely incorporatedherein by reference.

The tubes may be positioned in the furnace in any configuration.Preferably the tubes are positioned vertically so feedstock enters fromthe top of the reactor tubes and product leaves with reactor effluentexiting the bottom of the reactor tubes. Preferably, the reactor tubesare straight rather than having a coiled or curved path through theradiant furnace (although coiled or curved tubes may be used).Additionally, the tubes may have a cross section that is circular,elliptical, rectangular, and/or other known shapes. Advantageously, thetubes have a small cross sectional size to minimize cross sectionaltemperature gradients. However, decreasing the cross sectional size ofthe tubes increases the number of tubes for a given production rate.Therefore, an optimum tube size selection is preferably optimized withrespect to minimizing cross sectional temperature gradient andminimizing cost of construction. Suitable e cross sectional sizes (i.e.,diameters for the cylindrical tubes) may be from 1 cm to 20 cm, morepreferably from 2 cm to 15 cm, and most preferably from 3 cm to 10 cm.

The tubes are heated with radiant heat provided from at least one burnerlocated within a radiant section of the furnace. Any burner type knownin the art may be used such as ceiling, wall, and floor mounted burners.Preferably the burners are positioned to provide heat flux near thereactor tube inlet that is greater than heat flux near the exit of thereactor tubes. If the reactor tubes are vertically oriented, the burnersare preferably positioned near the top inlet of the reactor tubes havingflames burning in a downward direction along the length of the tubes.Orienting the burners near the top of the vertical reactor tube andfiring to downward provides heat flux near the reactor tube inlet (top)that is greater than the heat flux near the reactor tube outlet. Higherheating is desired near the reactor tube inlet, e.g., for providing theheat of reaction plus heat required to heat up feedstock to desiredreaction temperature. Sufficient spacing should be provided betweenburners and tubes to prevent hot spots; this offset can range between 30cm and 300 centimeters, but is preferably about 100 cm. Preferentially,burners are arranged on both sides of the tubes and tubes are separatedby 0.25 to 2.0 tube diameters to provide uniform heating of the tubes.

The furnace may optionally also comprise one or more shields positionedto block at least a portion of the burner flame's radiation from anoutlet portion of the reactor tube where less heat flux is desired toavoid greater than desired temperatures, e.g., temperatures promotingundesired coking and/or cracking that occurs with temperatures above thedesired conversion condition temperature range for a given catalyst,operating pressure, and residence time. If the reactor tube isvertically oriented with a down-firing burner, at least one shield maybe positioned to block a portion of flame radiation from a bottomportion of the reactor tube. Preferably, the shield is a flue gas ductfunctioning to conduct flue gas produced by the burner away from theradiant section of the furnace.

The reactor tubes contain a catalyst composition. The catalystcomposition may be coated on the reactor tube inner surface or may bepart of a fixed bed (which includes both random and structured beds) ofcatalyst within the tubes. Preferably the reactor tubes contain a fixedbed of catalyst composition and inert material. Suitable methods ofpacking and or designing fixed beds of reactor tubes include U.S. Pat.No. 8,178,075, which is incorporated herein by reference. The reactortubes may include at least one internal structure, e.g., concentricshells, to support the catalyst composition and/or reduce pressure dropwithin the reactor tube. The reactor tubes may comprise mixing internalstructures positioned within the reactor tubes providing mixing in theradial direction. The mixing internal structures may be positionedwithin a bed of catalyst composition or in portions of the reactor tubeseparating two or more zones of catalyst composition. The reactor tubesmay comprise fins or contours on the inside or outside of the reactortubes promoting heat transfer from the tube wall to the catalystcomposition. The fins or contours may be positioned to provide heat fluxnear the reactor tube inlet that is greater than heat flux near theoutlet of the reactor tubes. Examples of suitable internal structuresinclude a plurality of baffles, sheds, trays, tubes, rods, fins,contours, and/or distributors. These internal structures may be coatedwith catalyst. Suitable internal structures may be metallic or ceramic.Preferred ceramics are those having high thermal conductivity, e.g.,silicon carbide, aluminum nitride, boron carbide, and silicon nitride.

The temperature profile of the reaction zone may be manipulated bycontrolling the rate of heat input (based on hardware design, catalystloading, firing, etc). Notwithstanding, providing heat flux near thereactor tube inlet that is greater than heat flux near the reactor tubeoutlet, a substantially isothermal temperature profile may be provided,measured along the tube centerline. A substantially isothermaltemperature profile has the advantages of maximizing the effectiveutilization of the catalyst and minimizing the production of undesirableC⁴⁻ byproducts. As used herein, “isothermal temperature profile” meansthat the temperature at each point between the reactor inlet and reactoroutlet as measured along the tube centerline of the reactor is keptessentially constant, e.g., at the same temperature or within the samenarrow temperature range wherein the difference between an uppertemperature and a lower temperature is no more than about 40° C.; morepreferably no more than about 20° C. Preferably, the isothermaltemperature profile is one where the reactor inlet temperature is withinabout 40° C. of the reactor outlet temperature, alternately within about20° C., alternately within about 10° C., alternately within about 5° C.,alternately the reactor inlet temperature is the same as the reactoroutlet temperature. Alternately, the isothermal temperature profile isone where the reactor inlet temperature is within about 20% of thereactor outlet temperature, alternately within about 10%, alternatelywithin about 5%, alternately within about 1%.

Preferably, the isothermal temperature profile is one where thetemperature along the length of the reaction zone(s) within the reactordoes not vary by more than about 40° C. as compared to reactor inlettemperature, alternately not more than about 20° C., alternately notmore than about 10° C., alternately not more than about 5° C.Alternately, the isothermal temperature profile is one where thetemperature along the length of the reaction zone(s) within the reactoris within about 20% of the reactor inlet temperature, alternately withinabout 10%, alternately within about 5%, alternately within about 1% ofthe reactor inlet temperature.

However, to minimize catalyst deactivation rate it may be preferable tooptimize the radiant section and reactor tube design so that asubstantially inverse temperature profile is maintained in the reactortubes. As used herein, “inverse temperature profile” means that thereactor inlet temperature is lower than the reactor outlet temperature.Preferably, tube centerline temperature at the tube inlet is lower thanthe tube centerline temperature at the tube outlet. “Inverse temperatureprofile” includes systems where the temperature varies in the tube orsystems so long as the temperature at the reactor tube inlet is lowerthan the temperature at the reactor tube outlet. “Inverse temperatureprofile” further encompasses a reactor tube having a centerlinetemperature T1; at some length along the reactor tube, the centerlinetemperature decreases to temperature T2; at a further length along thereactor tube, the centerline temperature rises to temperature T3;finally, the centerline temperature at the reactor tube outlet decreasesto temperature T4; wherein T3>T4>T1>T2.

The temperature measured where feedstock first contacts catalystcomposition near the reactor inlet may be between about 0° C. to about200° C., preferably, about 25° C. to about 150° C., more preferablyabout 50° C. to about 100° C., lower than the temperature measured wherethe effluent leaves contact with catalyst composition near the reactoroutlet. Preferably, the tube centerline temperature measured wherefeedstock first contacts catalyst composition near the tube inlet may bebetween about 0° C. to about 200° C., preferably, about 25° C. to about150° C., more preferably about 50° C. to about 100° C., lower than thetube centerline temperature measured where the effluent leaves contactwith catalyst composition near the tube outlet.

Maintaining an inverse temperature profile in the reactor tube mayadvantageously minimize carbonaceous material formation at the inlet,which can contribute to coking of the catalyst composition. The inversetemperature profile may also provide sufficient reaction time and lengthin the reactor tube to produce a sufficient amount of H₂, at loweroperating temperatures than outlet temperature, which can minimizecarbonaceous material formation at the outlet for an effluent.

The conversion system furnace comprises a radiant section, a convectionsection, and a flue gas stack. Hot flue gas is generated by at least oneburner in the radiant section of the furnace and conducted away toatmosphere through the convection section and exiting the flue gasstack. Heat from the flue gas may be transferred by convection from theflue gas to heat a variety of streams, e.g., feedstock, steam, fuelpreheating, and/or combustion air preheating, passing through exchangersor tube bundles traversing the convection section. The furnaceconvection section may contain at least one exchanger or tube bundle inwhich flue gas heat is transferred by convection to feedstock and/orsteam.

The conversion system may further comprise multiple furnaces. Theconversion system may comprise two or more furnaces, each furnacecomprising a radiant section comprising parallel reactor tubescontaining catalyst composition. Optionally, the conversion systemcomprises a single convection section and flue gas stack in fluidcommunication with two or more furnace radiant sections.

Rejuvenation

During the conversion process, carbonaceous or coke material forms onthe catalyst composition, reducing the activity of the catalystcomposition. The amount of coke that is deposited on the catalystsduring a conversion cycle is referred to as the incrementally depositedcoke. A rejuvenation gas substantially free of reactiveoxygen-containing compounds and comprising hydrogen (H₂) is provided tothe reactor tubes. “Substantially free” used in this context means therejuvenation gas comprises less than about 1.0 wt. %, based upon theweight of the rejuvenation gas, e.g., less than about 0.1 wt. %, lessthan about 0.01 wt. %, less than about 0.001 wt. %, less than about0.0001 wt. %, less than about 0.00001 wt. % oxygen-containing compounds.“Reactive oxygen-containing compounds” are compounds where the oxygen isavailable to react with the catalyst as compared to inert compoundscontaining oxygen (such as CO), which do not react with the catalyst.

Flow of rejuvenation gas may be in the same or opposite direction to thediscontinued feedstock flow. The rejuvenation gas comprises ≧50 wt % H₂,such as ≧60 wt %, ≧70 wt %, preferably ≧90 wt % H₂. Rejuvenation gas mayfurther comprise an inert substance (e.g., N₂, CO), and/or methane.

The rejuvenation gas is contacted with the catalyst composition insidethe reactor tube forming light hydrocarbon and removing at least 10 wt %(≧10 wt %) of incrementally deposited coke material. Between about 10 wt% to about 100 wt %, preferably between about 90 wt % to about 100 wt %of incrementally deposited coke material is removed. Following cokematerial removal, flow of rejuvenation gas is halted and acyclic C₅feedstock flow is resumed.

Rejuvenation in the specified conversion system advantageously has atime duration of ≦90 mins, e.g., ≦60 mins, ≦30 mins, ≦10 mins, such as≦1 min, or ≦10 seconds. Contacting catalyst composition with therejuvenation gas occurs at a temperature of about 500° C. to about 900°C., preferably about 575° C. to about 750° C. The reactor tube outletpressure is between about 5 psia to about 250 psia, preferably about 25psia to about 250 psia during rejuvenation cycle. Rejuvenation may beadvantageously performed ≧10 minutes, e.g., ≧30 minutes, ≧2 hours, ≧5hours, ≧24 hours, ≧2 days, ≧5 days, ≧20 days, after beginning thespecified conversion process.

Rejuvenation effluent exiting the reactor tubes and comprising lighthydrocarbon, unreacted hydrogen, and coke particulate may be sent to acompression device and then sent to a separation apparatus wherein alight hydrocarbon enriched gas and light hydrocarbon depleted gas isproduced. The light hydrocarbon gas may be carried away, e.g., for useas fuel gas. The light hydrocarbon depleted stream may be combined withmake-up hydrogen and make up at least a portion of the rejuvenation gasprovided to the reactor tubes. The separation apparatus may be amembrane system, adsorption system (e.g., pressure swing or temperatureswing), or other known system for separation of hydrogen from lighthydrocarbons. A particulate separation device, e.g., a cyclonicseparation drum, may be provided wherein coke particulate is separatedfrom the effluent rejuvenation gas.

Regeneration

During the conversion process, some carbonaceous or coke material formson the catalyst composition that is not removed by oxygen freerejuvenation with H₂ containing rejuvenation gas. An oxidativeregeneration is used to remove at least a portion of this coke materialfrom the catalyst composition. The regeneration cycle begins bydiscontinuing flow of feedstock to the reactor tubes and purgingcombustible hydrocarbon gas, including feedstock or reactor product(acyclic and cyclic C₅ hydrocarbon), from the reactor tubes using apurge gas, for example, N₂. Following hydrocarbon purging, e.g., toconcentrations below combustible concentration limits, a regenerationgas comprising an oxidizing material such as oxygen, for example, air,is provided to the reactor tubes. Regeneration gas is contacted with thecatalyst composition inside the reactor tube to oxidatively remove atleast 10 wt % (≧10 wt %) of coke material present at the start ofregeneration. Between about 10 wt % to about 100 wt %, preferablybetween about 90 wt % to about 100 wt % of coke material is removed.Following coke material removal, flow of rejuvenation gas is halted andpurge gas is reintroduced to purge oxygen-containing regeneration gasfrom the reactor tubes, e.g., to a concentration below the combustibleconcentration limit. Subsequent to purging oxygen, flow of feedstock maybe resumed.

Regeneration, including purging before and after coke oxidation,requires less than 10 days, preferably less than about 3 days tocomplete. Regeneration may be performed between about once every 6 daysto about once every 180 days, preferably between about once every 10days to about once every 40 days.

Multiple Furnace Cycle Arrangement

The conversion system can comprise providing two or more furnaces, eachfurnace comprising parallel reactor tube(s). The reactor tubes comprisethe specified catalyst composition. The conversion process of thespecified conversion system can comprise providing a rejuvenation gas ora regeneration gas to one or more furnaces and, at the same time,providing feedstock comprising acyclic C₅ hydrocarbon to a different oneor more furnaces.

FIG. 1 illustrates an arrangement 220 for multiple furnacesinterconnected in parallel. Feedstock comprising C₅ hydrocarbons (e.g.,acyclic C₅ hydrocarbons) may be distributed to all the furnaces from onefeedstock header 201 (not all conduits from every header to everyreactor are shown in FIG. 1). Product may be collected from all thefurnaces via one product header 204. For information on possibledispositions of the collected product, please see applications:

1) U.S. Ser. No. 62/250,678, filed Nov. 4, 2015;

2) U.S. Ser. No. 62/250,692, filed Nov. 4, 2015;

3) U.S. Ser. No. 62/250,702, filed Nov. 4, 2015; and

4) U.S. Ser. No. 62/250,708, filed Nov. 4, 2015; which are incorporatedherein by reference.

Similarly, there may be one rejuvenation gas supply header 202 for therejuvenation gas and/or one regeneration gas supply header 200 forregeneration gas that is distributed to all the furnaces. A regenerationeffluent header 205 may collect regeneration effluent from all thefurnaces. Likewise, a rejuvenation effluent header 203 may collectrejuvenation effluent from all the furnaces. While an arrangement offour (4) furnaces is shown in FIG. 1, the invention is not limited bythis number. Arrangements of multiple furnaces having 2, 3, 4, 5, 6, 7,8, 9, 10, or more furnaces are suitable for the invention.

Feedstock comprising acyclic C₅ may be provided from feedstock header201 to at least one furnace, e.g., via conduit 206 to Furnace 210 and/orvia conduit 208 to Furnace 212, as part of the “on-oil” conversioncycle. Reactor effluent comprising cyclic C₅ product exiting the“on-oil” furnaces (e.g., via conduits 214 and/or 216) is combined andconducted away via common product header 204. Concurrent to the “on-oil”conversion, rejuvenation gas may be provided to one or more furnaces,e.g., via conduit 207 to Furnace 211. Similarly, regeneration gas andpurge gas may be provided concurrently to one or more furnaces throughregeneration gas supply header 200, e.g., via conduit 209 to Furnace213. Regeneration effluent may be collected from the one or morefurnaces provided regeneration gas and purge gas. For example,regeneration effluent may be collected from Furnace 213 via conduit 217to regeneration effluent header 205. Rejuvenation effluent may becollected from the one or more furnaces provided rejuvenation gas. Forexample, rejuvenation effluent may be collected from Furnace 211 viaconduit 215 to rejuvenation effluent header 203. Each furnace isdesigned with valving systems not shown to enable connection to andisolation from all the various headers dependent on whether the reactoris in use for on-oil feedstock conversion, rejuvenation, and/orregeneration cycles. The figure indicates flows at a specific point intime. It should be recognized that at other points in time the flows maydepart from those shown in the figure as reactors may periodically beexposed to on-oil feedstock conversion, rejuvenation, and/orregeneration cycles. Any valving system and control system known in theart may be used, e.g., double block and bleed to prevent contacting offlammable gases and oxidant gases.

Advantageously, the conversion process can comprise a cyclic arrangementfor concurrent “on-oil” feedstock conversion, rejuvenation, and/orregeneration in a multiple furnace conversion system. “On-oil”conversion time is typically greater than 10 minutes, often from about10 minutes to about 20 days. Rejuvenation time is typically from about10 seconds to about 2 hours. The arrangement 220 indicated in FIG. 1allows multiple furnaces, e.g., Furnace 210, 211, and 212, may repeat arotating cycle “on-oil” conversion and rejuvenation while at least oneother furnace, e.g., Furnace 213, completes regeneration. Whenregeneration of a furnace, e.g., Furnace 213, is complete, it may bereturned to “on-oil” conversion/rejuvenation cycle while anotherfurnace, e.g., Furnace 210, may be cycled out for regeneration asrequired. Advantageously, such an arrangement provides more consistentproduct composition while reducing the amount of equipment needed.

FURTHER EMBODIMENTS

This invention further relates to:

Embodiment 1

A process for converting acyclic C₅ hydrocarbon to cyclic C₅ hydrocarbonincluding cyclopentadiene, wherein the process comprises:

a) providing a furnace comprising parallel reactor tube(s), the reactortubes containing catalyst composition;

b) providing feedstock comprising acyclic C₅ hydrocarbon;

c) contacting the feedstock with the catalyst composition; and

d) obtaining a reactor effluent comprising cyclic C₅ hydrocarbonwherein, the cyclic C₅ hydrocarbon comprises cyclopentadiene.

Embodiment 2

The process of Embodiment 1, wherein i) the reactor tubes are positionedvertically so the feedstock is provided from the top and the reactoreffluent exits from the bottom and ii) the furnace comprises at leastone burner positioned near the top of the reactor tubes having a flameburning in a downward direction providing heat flux near the top that isgreater than heat flux near the bottom of the reactor tubes.

Embodiment 3

The process of Embodiment 1 or 2, wherein a shield blocks at least aportion of the burner flame's radiation from a bottom portion of thereactor tube.

Embodiment 4

The process of Embodiment 3, wherein the shield is a flue gas duct.

Embodiment 5

The process of any of Embodiments 1-4, wherein the reactor tubes have aninverse temperature profile.

Embodiment 6

The process of any of Embodiments 1-5, wherein the contacting feedstockand catalyst composition is performed in the presence of a gascomprising H₂ and/or C₁ to C₄ hydrocarbons.

Embodiment 7

The process of any of Embodiments 1-6, further comprising promoting heattransfer from the tube wall to the catalyst composition by providingfins or contours on the inside or outside of the reactor tubes.

Embodiment 8

The process of any of Embodiments 1-7, further comprising mixingfeedstock and converted cyclic C₅ hydrocarbon in the radial direction byproviding mixing internals within the reactor tubes, wherein the mixinginternals are positioned i) within a bed of the catalyst composition orii) in portions of the reactor tube separating two or more zones ofcatalyst composition.

Embodiment 9

The process of any of Embodiments 1-8, wherein contacting step c) occursat a temperature of about 450° C. to about 800° C.

Embodiment 10

The process of any of Embodiments 1-9, wherein the feedstock provided tothe inlet of the reactor tubes has a temperature of about 450° C. toabout 550° C.

Embodiment 11

The process of any of Embodiments 1-10, wherein the reactor tubes havean outlet pressure of about 4 psia to about 50 psia during contactingstep c).

Embodiment 12

The process of any of Embodiments 1-11, wherein the reactor tubes have apressure drop measured from reactor inlet to reactor outlet from about 1psi to about 100 psi during contacting feedstock with catalystcomposition.

Embodiment 13

The process of any of Embodiments 1-12, wherein at least about 30 wt %of the acyclic C₅ hydrocarbons is converted to cyclopentadiene.

Embodiment 14

The process of any of Embodiments 1-13, wherein the catalyst compositioncomprises platinum on ZSM-5, platinum on zeolite L, and/or platinum onsilicate modified silica.

Embodiment 15

The process of Embodiment 14, wherein the catalyst composition furthercomprises an inert material.

Embodiment 16

The process of any of Embodiments 1-15, wherein the catalyst compositionis an extrudate having a diameter of 2 mm to 20 mm.

Embodiment 17

The process of any of Embodiments 1-16, wherein the catalyst compositioncross section is shaped with one or more lobes and/or concave sections.

Embodiment 18

The process of Embodiment 17, wherein the catalyst composition lobesand/or concave sections are spiraled.

Embodiment 19

The process of any of Embodiments 1-18, wherein the weight hourly spacevelocity based on active catalyst content in the reactor tube is from 1to 1000 hr⁻¹.

Embodiment 20

The process of any of Embodiments 1-19, wherein the inside diameter ofthe reactor tubes is from about 20 mm to about 200 mm.

Embodiment 21

The process of any of Embodiments 1-20, wherein i) the feedstock, aregeneration gas, or a rejuvenation gas is conducted to and from thereactor tubes through inlet and outlet manifolds.

Embodiment 22

The process of any of Embodiments 1-21, further comprising transferringheat by convection from flue gas to rejuvenation gas, regeneration gas,steam, and/or the feedstock in a convection section of the furnace.

Embodiment 23

The process of any of Embodiments 1-22, further comprising i) providingtwo or more furnaces, each furnace comprising parallel reactor tube(s),the reactor tubes containing catalyst composition and ii) providing arejuvenation gas or a regeneration gas to one or more furnaces and, atthe same time, providing feedstock comprising acyclic C₅ hydrocarbons toa different one or more furnaces.

Embodiment 24

The process of any of Embodiments 1-23 further comprising:

a) discontinuing providing a feedstock comprising acyclic C₅hydrocarbons;

b) providing a rejuvenation gas comprising H₂;

c) contacting the rejuvenation gas with the catalyst composition toremove at least a portion of coke material on the catalyst composition;and

d) discontinuing providing a rejuvenation gas and resuming providing afeedstock comprising acyclic C₅ hydrocarbons.

Embodiment 25

The process of Embodiment 24, wherein the time duration of steps athrough d is 1.5 hours or less.

Embodiment 26

The process of Embodiments 24 or 25, wherein contacting rejuvenation gasoccurs at a temperature of about 500° C. to about 900° C.

Embodiment 27

The process of any of Embodiments 24-26, wherein the reactor tubes havean outlet pressure of about 5 psia to about 250 psia during contactingrejuvenation gas.

Embodiment 28

The process of any of Embodiments 24-27, wherein contacting rejuvenationgas occurs at a temperature of about 575° C. to about 750° C.

Embodiment 29

The process of any of Embodiments 24-28, wherein the reactor tubes havean outlet pressure of about 25 psia to about 250 psia during contactingrejuvenation gas.

Embodiment 30

The process of any of Embodiments 24-29, wherein at least a portion ofthe coke material is incrementally deposited and at least 10 wt % of theincrementally deposited coke material is removed from the catalystcomposition.

Embodiment 31

The process of any of Embodiments 1-30 further comprising:

a) discontinuing providing a feedstock comprising acyclic C₅hydrocarbons;

b) purging any combustible gas, including feedstock and reactor product,from the reactor tubes;

c) contacting a regeneration gas comprising an oxidizing material withthe catalyst composition to oxidatively remove at least a portion ofcoke material on the catalyst composition;

d) purging regeneration gas from the reactor tubes; and

e) discontinuing purging of regeneration gas and resuming providing afeedstock comprising acyclic C₅ hydrocarbons.

Embodiment 32

A conversion system for converting acyclic C₅ hydrocarbon to cyclic C₅hydrocarbon, wherein the conversion system comprises:

a) a feedstock stream comprising acyclic C₅ hydrocarbon;

b) a furnace comprising parallel reactor tube(s), the reactor tubescontaining catalyst composition; and

c) a reactor effluent stream comprising cyclic C₅ hydrocarbon producedby contacting the feedstock with the catalyst composition, wherein thecyclic C₅ hydrocarbon comprises cyclopentadiene.

Embodiment 33

The system of Embodiment 32, wherein i) the reactor tubes are positionedvertically, the feedstock is provided from the top, and the reactoreffluent exits from the bottom of the reactor tubes and ii) the furnacefurther comprises at least one burner positioned near the top of thereactor tubes having a flame burning in a downward direction providingheat flux near the top that is greater than heat flux near the bottom ofthe reactor tubes.

Embodiment 34

The system of Embodiments 32 or 33, further comprising a shield blockingat least a portion of the burner flame's radiation from a bottom portionof the reactor tubes.

Embodiment 35

The system of Embodiment 34, wherein the shield is a flue gas duct.

Embodiment 36

The system of any of Embodiments 32-35, further comprising a gas streamcomprising H₂ and/or C₁ through C₄ hydrocarbons.

Embodiment 37

The system of any of Embodiments 32-36, further comprising fins orcontours on the inside or outside of the reactor tubes promoting heattransfer from the tube wall to the catalyst composition.

Embodiment 38

The system of any of Embodiments 32-37, further comprising mixinginternals positioned within the reactor tubes providing mixing in theradial direction, wherein the mixing internals are positioned i) withina bed of the catalyst composition or ii) in portions of the reactor tubeseparating two or more zones of catalyst composition.

Embodiment 39

The system of any of Embodiments 32-38, wherein the catalyst compositioncomprises platinum on ZSM-5, platinum on zeolite L, and/or platinum onsilica.

Embodiment 40

The system of Embodiment 39, wherein the catalyst composition furthercomprises an inert material.

Embodiment 41

The system of any of Embodiments 32-40, wherein the catalyst compositionis an extrudate with a diameter of 2 mm to 20 mm.

Embodiment 42

The system of any of Embodiments 32-41, wherein the catalyst compositioncross section is shaped with one or more lobes and/or concave sections.

Embodiment 43

The system of Embodiment 42, wherein the catalyst composition lobesand/or concave sections are spiraled.

Embodiment 44

The system of any of Embodiments 32-43, wherein the diameter of thereactor tubes is from about 20 mm to about 200 mm.

Embodiment 45

The system of any of Embodiments 32-44, further comprising inlet andoutlet manifolds in fluid communication with the reactor tubes whereinthe feedstock, a regeneration gas, or a rejuvenation gas is conducted toand from the reactor tubes through the inlet and outlet manifolds.

Embodiment 46

The system of any of Embodiments 32-45, wherein the furnace furthercomprises a convection section providing indirect heat transfer byconvection from flue gas to rejuvenation gas, regeneration gas, steam,and/or the feedstock.

Embodiment 47

The system of any of Embodiments 32-46, further comprising an additionalone or more furnaces, each furnace comprising parallel reactor tube(s),the reactor tubes containing catalyst composition, enabling providing arejuvenation gas or a regeneration gas to one or more furnaces and, atthe same time, providing the feedstock comprising acyclic C₅hydrocarbons to a different one or more furnaces.

Embodiment 48

The system of any of Embodiments 32-47, further comprising:

a) a rejuvenation gas stream comprising H₂; and

b) a means for contacting the rejuvenation gas with the catalystcomposition to remove at least a portion of coke material on thecatalyst composition.

Embodiment 49

The system of any of Embodiments 32-48, further comprising:

a) a purge stream comprising an inert gas and a regeneration gas streamcomprising an oxidizing material; and

b) a means for i) purging any combustible gas, including feedstock andreactor product, from the reactor tubes and ii) contacting theregeneration gas with the catalyst composition to oxidatively remove atleast a portion of coke material on the catalyst composition.

INDUSTRIAL APPLICABILITY

The first hydrocarbon reactor effluent obtained during the acyclic C₅conversion process containing cyclic, branched, and linear C₅hydrocarbons and, optionally, containing any combination of hydrogen, C₄and lighter byproducts, or C₆ and heavier byproducts is a valuableproduct in and of itself. Preferably, CPD and/or DCPD may be separatedfrom the reactor effluent to obtain purified product streams, which areuseful in the production of a variety of high value products.

For example, a purified product stream containing 50 wt % or greater, orpreferably 60 wt % or greater of DCPD is useful for producinghydrocarbon resins, unsaturated polyester resins, and epoxy materials. Apurified product stream containing 80 wt % or greater, or preferably 90wt % or greater of CPD is useful for producing Diels-Alder reactionproducts formed in accordance with the following reaction Scheme (I):

where R is a heteroatom or substituted heteroatom, substituted orunsubstituted C₁-C₅₀ hydrocarbyl radical (often a hydrocarbyl radicalcontaining double bonds), an aromatic radical, or any combinationthereof. Preferably, substituted radicals or groups contain one or moreelements from Groups 13-17, preferably from Groups 15 or 16, morepreferably nitrogen, oxygen, or sulfur. In addition to the monoolefinDiels-Alder reaction product depicted in Scheme (I), a purified productstream containing 80 wt % or greater, or preferably 90 wt % or greaterof CPD can be used to form Diels-Alder reaction products of CPD with oneor more of the following: another CPD molecule, conjugated dienes,acetylenes, allenes, disubstituted olefins, trisubstituted olefins,cyclic olefins, and substituted versions of the foregoing. PreferredDiels-Alder reaction products include norbornene, ethylidene norbornene,substituted norbornenes (including oxygen-containing norbornenes),norbornadienes, and tetracyclododecene, as illustrated in the followingstructures:

The foregoing Diels-Alder reaction products are useful for producingpolymers and copolymers of cyclic olefins copolymerized with olefinssuch as ethylene. The resulting cyclic olefin copolymer and cyclicolefin polymer products are useful in a variety of applications, e.g.,packaging film.

A purified product stream containing 99 wt % or greater of DCPD isuseful for producing DCPD polymers using, for example, ring openingmetathesis polymerization (ROMP) catalysts. The DCPD polymer productsare useful in forming articles, particularly molded parts, e.g., windturbine blades and automobile parts.

Additional components may also be separated from the reactor effluentand used in the formation of high value products. For example, separatedcyclopentene is useful for producing polycyclopentene, also known aspolypentenamer, as depicted in Scheme (II).

Separated cyclopentane is useful as a blowing agent and as a solvent.Linear and branched C₅ products are useful for conversion to higherolefins and alcohols. Cyclic and non-cyclic C₅ products, optionallyafter hydrogenation, are useful as octane enhancers and transportationfuel blend components.

EXAMPLES

The following examples illustrate the present invention. Numerousmodifications and variations are possible and it is to be understoodthat within the scope of the appended claims, the invention may bepracticed otherwise than as specifically described herein.

Example 1

Referring to FIG. 2, a feedstock 10 comprising acyclic C₅ hydrocarbon isprovided to parallel reactor tube(s) 23 in radiant section 21 of furnace20. The feedstock is contacted with catalyst composition (not shown)inside reactor tubes 23. A reactor effluent 32 comprising cyclic C₅hydrocarbon (e.g., cyclopentadiene) is conducted away as a product orfor further processing. Reactor tubes 23 are positioned in a verticalorientation (vertically) so feedstock 10 enters reactor tubes from thetop and reactor effluent 32 exits the reactor tubes from the bottom.Burners 24 are positioned near the top of the reactor tubes so that theburners' flames burn in a downward direction providing heat flux nearthe top of the reactor tubes 23 that is greater than heat flux near thebottom of the reactor tubes 23. Shield 25 blocks at least a portion ofthe burners 24 flames' radiation from a bottom portion of the reactortubes 23. Shield 25 further functions as a flue gas duct through whichflue gas (not shown) produced by burners 24 is conducted away fromradiant section 21 to convection section 22 of furnace 20. Convectiveheat from the flue gas is transferred within convection section 22 toheat i) the feedstock 10 in exchanger 12, ii) rejuvenation orregeneration gas 41 in exchanger 42, and iii) steam 60 in exchanger 61.Heated steam produced in exchanger 61 is conducted away via conduit 62for, among other uses, further use as a utility stream. Flue gas (notshown) exits furnace 20 via stack 26.

Feedstock 10 is conducted via conduit 11 to exchanger 12 is preheated toabout 450° C. to about 550° C. and conducted from exchanger 12 toreactor tubes 23 via conduit 13, inlet manifold 14 and conduit 15. Thefeedstock 10 is contacted with catalyst composition (not shown) at about450° C. to about 800° C. in reactor tubes 23. The reactor tubes 23 areheated by burners 24 so the reactor tubes have a tube centerlineinternal temperature that increases with tube length from inlet tooutlet. The outlet pressure of the reactor tubes 23 is maintainedbetween about 4 psia to about 50 psia during contacting. Feedstock 10and converted cyclic C₅ hydrocarbon (e.g., cyclopentadiene) are mixed inthe radial direction by mixing internals (not shown) inside the reactortubes 23. At least about 30 wt % of the acyclic C₅ hydrocarbons infeedstock 10 is converted to cyclopentadiene. The pressure drop acrossthe reactor tubes 23 is about 1 psi to about 100 psi during contacting.

Flow of feedstock 10 may be discontinued to conduct rejuvenation. Arejuvenation gas 45 comprising H₂ is provided via rejuvenation system 40and conduit 41. Rejuvenation gas 45 is optionally heated with convectiveheat in exchanger 42 and conducted to reactor tubes 23 via conduit 43,inlet manifold 14, and conduit 15. Rejuvenation gas 45 is contacted withthe catalyst composition (not shown) inside reactor tube 23 at about400° C. to about 800° C. to remove at least a portion of coke material(not shown) from the catalyst composition. The outlet pressure ofreactor tubes 23 is about 5 psia to about 250 psia during contactingwith rejuvenation gas 45. At least 10 wt % of the incrementallydeposited coke material is removed from the catalyst composition.

Rejuvenation effluent exits reactor tubes 23 and is conducted away torejuvenation system 40 via conduit 30, outlet manifold 31, and conduit44. Within rejuvenation system 40, the rejuvenation effluent comprisinglight hydrocarbon, unreacted hydrogen, and coke particulate is sent to acompression device (not shown) and then sent to a separation apparatus(also not shown) wherein a light hydrocarbon enriched gas and lighthydrocarbon depleted gas is produced. The light hydrocarbon gas (notshown) is carried away for use, among other things, as fuel gas. Thelight hydrocarbon depleted stream (also not shown) is combined withfresh rejuvenation gas 45 in rejuvenation system 40 and provided to thereactor tubes. Following sufficient coke removal, the flow ofrejuvenation gas 45 is discontinued and providing feedstock 10 isresumed.

Flow of feedstock 10 may be discontinued to conduct regeneration. Apurge gas 54 is provided via regen system 50, conduit 51, inlet manifold14, and conduit 15. Flow of purge gas 54 is provided to purge anycombustible gas, including feedstock and reactor product, from thereactor tubes 23 and related conduits and manifolds. Following purging,regeneration gas 53 comprising an oxidizing material, e.g., air, isprovided via regen system 50 and conduit 51. Regeneration gas 53 isconducted to reactor tubes 23 via conduit 51, inlet manifold 14, andconduit 15. Regeneration gas 53 is contacted with the catalystcomposition (not shown) inside reactor tube 23 to remove at least aportion of coke material (not shown) from the catalyst composition byoxidation with the regeneration gas 53. Regeneration effluent exitsreactor tubes 23 and is conducted away to regen system 50 via conduit30, outlet manifold 31, and conduit 52. When sufficient coke has beenremoved, e.g., at least 10 wt % of coke has been removed or when nofurther oxidation is detected by low concentration of oxidationproducts, such as CO or CO₂ leaving the reactor tubes 23, the flow ofregeneration gas 53 is discontinued. Flow of purge gas 54 is resumed topurge regeneration gas from the reactor tubes 23. Following purging flowof feedstock 10 is resumed.

Example 2

A mixture with ˜22% solids was prepared by mixing 8,800 g of DI water,600 g of 50% NaOH solution, 26 g of 43% Sodium Aluminate solution, 730 gof n-propyl amine 100% solution, 20 g of ZSM-5 seed crystals, and 3,190g of Sipernat-340 silica in a 5-gal pail container. The mixture was thencharged into a 5-gal autoclave. The mixture had the following molarcomposition:

SiO₂/Al₂O₃ ~470 H₂O/SiO₂ ~10.7 OH/SiO₂ ~0.16 Na/SiO₂ ~0.16 n-PA/Si~0.25.

In the autoclave, the mixture was mixed at 350 rpm and reacted at 210°F. (99° C.) for 72 hours. The resulting reaction slurry was dischargedand stored in a 5-gal pail container. The XRD pattern (not shown) of theas-synthesized material showed the typical pure phase of ZSM-5 topology.The SEM (not shown) of the as-synthesized material shows that thematerial was composed of a mixture of crystals with a size of 0.5-1micron. The as-synthesized crystals had a SiO₂/Al₂O₃ molar ratio of ˜467and Na of ˜0.25 wt %.

This material was calcined for 6 hours in nitrogen at 900° F. (482° C.).After cooling, the sample was re-heated to 900° F. (482° C.) in nitrogenand held for three hours. The atmosphere was then gradually changed to1.1, 2.1, 4.2, and 8.4% oxygen in four stepwise increments. Each stepwas followed by a thirty minute hold. The temperature was increased to1000° F., the oxygen content was increased to 16.8%, and the materialwas held at 1000° F. for 6 hours. After cooling, 0.29 wt % Ag was addedvia incipient wetness impregnation using an aqueous solution of silvernitrate. The sample was dried for four hours at 250° F. (120° C.).Subsequently, 0.44 wt % Pt was added via incipient wetness impregnationusing an aqueous solution of tetraamine platinum hydroxide. The catalystwas dried in air at room temperature, then at 250° F. (120° C.), andcalcined in air for one hour at 610° F. (320° C.).

Example 3

The catalyst of Example 2 was tested under two reactor temperatureprofiles: a substantially isothermal temperature profile and an inversetemperature profile. The catalyst (0.5 g) was physically mixed withquartz (1.5 g, 60-80 mesh) and loaded into a ⅜″ OD, 18″ long stainlesssteel reactor. The catalyst bed was held in place with quartz wool andthe reactor void space was loaded with coarse quartz particles. Thecatalyst was dried for 1 hour under He (100 mL/min, 30 psig, 250° C.)then reduced for 1 hour under H2 (200 mL/min, 30 psig, 500° C.). Thecatalyst was then tested for performance with a feed containingn-pentane, H2, and balance He.

The test conditions for maintaining an isothermal temperature profilewere the following: 0.5 g ZSM-5(400:1)/0.4% Pt/0.2% Ag, 5 psia C5H12 atreactor inlet, 1:1 H2:C5 feed, and 60 psia total pressure with Hebalance, WHSV was 16.1 h-1, 600° C. bed temperature. The test conditionsfor maintaining an inverse temperature profile were the following: 0.5 gZSM-5(400:1)/0.4% Pt/0.2% Ag, 5 psia C5H12 at reactor inlet, 1:1 H2:C5feed, and 60 psia total pressure with He balance, WHSV was 4.0 h-1 forthe gradient experiment and a linear temperature gradient of 500 to 600°C. was applied. The performance results of Example 3 are shown in FIGS.4 and 5.

As shown in FIG. 3, a reactor operating with an inverse or gradienttemperature profile (i.e., a lower temperature at the inlet and a highertemperature at the outlet), results in a catalyst having higherstability over that of a reactor operating isothermally at the sameoutlet temperature. Specifically, FIG. 3 shows that while the totalcyclic C₅ hydrocarbon yield for both temperature profiles was similarinitially, the yield decreased to 43% of its original value over 53hours in the reactor having an isothermal temperature profile. Incontrast, the yield in an inverse temperature profile operating regimeonly decreased to 73% of its original value, and this decline in yieldoccurred over a longer timeframe of 57 hours. As shown in FIG. 4, areactor operating isothermally can be beneficial over that operatingwith an inverse or gradient temperature profile when it is desired tominimize the yield of byproduct C1-C4 cracked hydrocarbon products.

Example 4

A mixture with ˜22% solids was prepared by mixing 950 g of DI water,53.5 g of 50% NaOH solution, 76.8 g of n-propyl amine 100% solution, 10g of ZSM-5 seed crystals, and 336 g of Ultrasil PM™ Modified silica, and4.4 g of Silver Nitrate in a 2-liter container. The mixture was thencharged into a 2-liter autoclave. The mixture had the following molarcomposition:

SiO2/Al2O3 >1000 H2O/SiO2 ~10.98 OH/SiO2 ~0.17 Na/SiO2 ~0.17 n-PA/Si~0.25.

In the autoclave, the mixture was mixed at 250 rpm and reacted at 230°F. (110° C.) for 72 hours. The resulting products were filtered andwashed with deionized water then dried overnight at 250° F. The XRDpattern (not shown) of the as-synthesized material showed the typicalpure phase of ZSM-5 topology. The SEM (not shown) of the as-synthesizedmaterial shows that the material was composed of a mixture of largecrystals with a size of <1 micron. The resulting ZSM-5 crystals had aSiO₂/Al₂O₃ molar ratio of >800, Na of ˜0.28%, and Ag of 0.9 wt %.

This material was calcined for 6 hours in nitrogen at 900° F. Aftercooling, the sample was re-heated to 900° F. in nitrogen and held forthree hours. The atmosphere was then gradually changed to 1.1, 2.1, 4.2,and 8.4% oxygen in four stepwise increments. Each step was followed by athirty minute hold. The temperature was increased to 1000° F., theoxygen content was increased to 16.8%, and the material was held at1000° F. for 6 hours. After cooling, 0.45 wt % Pt was added viaincipient wetness impregnation using an aqueous solution of tetraamineplatinum hydroxide. The catalyst was dried in air at room temperaturethen at 250° F., and calcined in air for three hours at 660° F. Thecatalyst powder was pressed (15 ton), crushed, and sieved to obtain40-60 mesh particle size.

Example 5

The catalyst of Example 4 was tested under two reactor operatingstrategies: a continuously on-oil strategy and an intermittent H2rejuvenation strategy. The catalyst (0.5 g) was physically mixed withquartz (1.5 g, 60-80 mesh) and loaded into a ⅜″ OD, 18″ long stainlesssteel reactor. The catalyst bed was held in place with quartz wool andthe reactor void space was loaded with coarse quartz particles. Thecatalyst was dried for 1 hour under He (100 mL/min, 30 psig, 250° C.)then reduced for 1 hour under H2 (200 mL/min, 30 psig, 500° C.). Thecatalyst was then tested for performance with a feed containingn-pentane, H2, and balance He. The test conditions for a continuouslyon-oil operating strategy were the following: 0.5 g [0.96%Ag]-ZSM-5/0.5% Pt, 5.0 psia C5H12, 1:1 molar H2:C5, 14.7 WHSV, 45 psiatotal during the on-oil period. The test conditions for an intermittentH2 rejuvenation strategy were the following: the reactor was cycled forone hour on-oil and one hour on H2 rejuvenation at the conditions of 200cm³ min⁻¹ H2 at 600° C. and 45 psia of all H2; i.e., with no additionalHe. Performance results for both operating strategies are shown in FIG.5 as the site-time-yield of cyclic C5's (i.e., the mols of cC5/mol ofPt/second). FIG. 5 demonstrates that the H2 rejuvenation is capable ofimproving catalyst capability over time to catalyze C5 hydrocarboncyclization.

All documents described herein are incorporated by reference herein,including any priority documents and/or testing procedures to the extentthey are not inconsistent with this text. As is apparent from theforegoing general description and the specific embodiments, while formsof the invention have been illustrated and described, variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited thereby. Likewise, the term “comprising” is consideredsynonymous with the term “including.” Likewise, whenever a composition,an element or a group of elements is preceded with the transitionalphrase “comprising,” it is understood that we also contemplate the samecomposition or group of elements with transitional phrases “consistingessentially of,” “consisting of,” “selected from the group of consistingof,” or “is” preceding the recitation of the composition element, orelements and vice versa.

What is claimed is:
 1. A process for converting acyclic C5 hydrocarbonto cyclic C5 hydrocarbon comprising: a) providing a furnace comprisingparallel reactor tube(s), the reactor tubes containing catalystcomposition, wherein the catalyst composition comprises platinum onZSM-5, platinum on zeolite L, and/or platinum on silicate modifiedsilica; b) providing a feedstock comprising acyclic C5 hydrocarbon; c)contacting the feedstock with the catalyst composition; d) obtaining areactor effluent comprising cyclic C5 hydrocarbon, wherein the cyclic C5hydrocarbon comprises cyclopentadiene; e) discontinuing providing saidfeedstock comprising acyclic C5 hydrocarbons; f) providing arejuvenation gas comprising H₂; g) contacting the rejuvenation gas withthe catalyst composition to remove at least a portion of coke materialon the catalyst composition; and h) discontinuing providing arejuvenation gas and resuming providing said feedstock comprisingacyclic C5 hydrocarbons.
 2. The process of claim 1, wherein i) thereactor tubes are positioned vertically so the feedstock is providedfrom the top and the reactor effluent exits from the bottom and ii) thefurnace comprises at least one burner positioned near the top of thereactor tubes having a flame burning in a downward direction providingheat flux near the top that is greater than heat flux near the bottom ofthe reactor tubes.
 3. The process of claim 2, wherein a shield blocks atleast a portion of the burner flame's radiation from a bottom portion ofthe reactor tube.
 4. The process of claim 3, wherein the shield is aflue gas duct.
 5. The process of claim 1, wherein the reactor tubes havean inverse temperature profile or an isothermal temperature profile. 6.The process of claim 1, wherein the contacting feedstock and catalystcomposition is performed in the presence of a gas comprising H₂ and/orC₁ through C₄ hydrocarbons.
 7. The process of claim 1, furthercomprising promoting heat transfer from the tube wall to the catalystcomposition by providing fins or contours on the inside or outside ofthe reactor tubes.
 8. The process of claim 1, further comprising mixingfeedstock and converted cyclic C₅ hydrocarbon in the radial direction byproviding mixing internals within the reactor tubes, wherein the mixinginternals are positioned i) within a bed of the catalyst composition orii) in portions of the reactor tube separating two or more zones ofcatalyst composition.
 9. The process of claim 1, wherein contacting stepc) occurs at a temperature of about 450° C. to about 800° C.
 10. Theprocess of claim 1, wherein the feedstock provided to the inlet of thereactor tubes has a temperature of about 450° C. to about 550° C. 11.The process of claim 1, wherein the reactor tubes have an outletpressure of about 4 psia to about 50 psia during contacting step c). 12.The process of claim 1, wherein the reactor tubes, during contactingfeedstock with catalyst composition, have a pressure drop measured fromreactor inlet to reactor outlet from about 1 psi to about 100 psi. 13.The process of claim 1, wherein at least about 30 wt % of the acyclic C₅hydrocarbons is converted to cyclopentadiene.
 14. The process of claim1, wherein the catalyst composition is an extrudate having a diameter of2 mm to 20 mm.
 15. The process of claim 1, wherein the catalystcomposition cross section is shaped with one or more lobes and/orconcave sections, and wherein the catalyst composition lobes and/orconcave sections are spiraled or straight.
 16. The process of claim 1,wherein the inside diameter of the reactor tubes is from about 20 mm toabout 200 mm.
 17. The process of claim 1, further comprisingtransferring heat by convection from flue gas to rejuvenation gas,regeneration gas, steam, and/or the feedstock in a convection section ofthe furnace.
 18. The process of claim 1, further comprising i) providingtwo or more furnaces, each furnace comprising parallel reactor tube(s),the reactor tubes containing catalyst composition and ii) providing arejuvenation gas or a regeneration gas to one or more furnaces and, atthe same time, providing feedstock comprising acyclic C₅ hydrocarbons toa different one or more furnaces.
 19. The process of claim 1 furthercomprising: a) discontinuing providing a feedstock comprising acyclic C₅hydrocarbons; b) purging combustible gas, including feedstock andreactor product, from the reactor tubes to a concentration below thecombustible concentration limit; c) contacting a regeneration gascomprising an oxidizing material with the catalyst composition tooxidatively remove at least a portion of coke material on the catalystcomposition; d) purging regeneration gas from the reactor tubes to aconcentration below the combustible concentration limit; and e)discontinuing purging of regeneration gas and resuming providing afeedstock comprising acyclic C₅ hydrocarbons.
 20. The process of claim1, wherein the catalyst composition is formed into a structured catalystshape.
 21. The process of claim 1, further comprising providing thefeedstock to at least one adiabatic reaction zone prior to thecontacting of c).